可调谐DFB半导体激光器的甲烷检测传感器

Methane Detection Sensor Based on Tunable DFB Semiconductor Laser

为提高甲烷浓度的检测精度,根据红外吸收光谱检测原理,推导了气体浓度跟二次谐波与一次谐波之比的关系,并利用可调谐DFB半导体激光器设计了甲烷浓度检测传感器。通过1 kHz的正弦电流叠加到激光器的电源进行调制,使光束扫描波长为3.312μm处的吸收峰,从而在碲镉汞红外探测器上产生谐波信号。同时,利用相敏检波技术设计了微弱信号处理电路,通过前置放大、带通滤波、相敏检波、直流放大等有效抑制了信道噪声,实现了对一次和二次谐波的高精度提取。实验结果表明:设计的甲烷浓度检测传感器具有较高的测量精度和稳定度,在0%~20%的量程上,最大误差不超过0.65%,平均误差仅为0.41%,可应用于在煤矿开采和化工生产中对甲烷泄漏的监测。

To improve the detection accuracy of methane concentration,the relationship between gas concentration and the ratio of second harmonic and first harmonic is deduced according to the principle of infrared absorption spectrum.A methane concentration detection sensor is designed by using tunable DFB semiconductor laser,superimposing a 1 kHz sinusoidal current on the power supply of the laser so that the laser beam can scan the absorption peak at 3.312μm,and the HgCdTe infrared detector can generate harmonic signals.Meantime,the weak signal processing circuit is designed by using phase-sensitive detection technology.The channel noise is effectively suppressed through preamplifier,bandpass filter,phase-sensitive detection and DC amplifier,and the high-precision extraction of first and second harmonics is realized.The experimental results show that the designed methane concentration sensor has high measurement accuracy and stability,the maximum error is not more than 0.65% and the average error is only 0.41%in the range of 0.20%,which can be used to monitor methane leakage in coal mining and chemical production.